1. Field of the Invention
The present invention belongs to the field of well pumping equipment and is used to control the operation of an artificial lift apparatus, such as a pumpjack, on an operating well.
2. Discussion of the Prior Art
The problems of efficiently operating the pumpjack of an operating oil well, which includes spacing out a down hole pump, gas-lock pounding, as well as fluid pressure pounding conditions have long been concerns in the field of the present invention. However, an economical and easily operated manner of reasons.
When a down-hole sucker rod pump gas locks, the common procedure is to lower the rod string until the rods are pounding bottom. This was accomplished by repositioning the top polish rod clamp four to six inches above the lower polish rod clamp and then loosening the nuts on the bottom polish rod clamp until the rod string "drops" that four to six inches. This process is repeated until the rods are lowered the correct amount. On an 8500-foot well, the typical rod string weighs approximately fourteen thousand pounds, or seven tons. Of course, if the well is deeper the weight increases, or if the well is not as deep the weight decreases. When fourteen thousand pounds is allowed to free-fall four to six inches and then suddenly stops, the resulting shock and stress to the rod string and surface equipment is tremendous.
If the top clamp should fail to stop the downward movement of the rod string, the shock is absorbed by the downhole equipment, which may cause the tubing string to break, the rod string to corkscrew, and/or the pump to be damaged. Great expense is then incurred to retrieve the damaged equipment from the well. In addition, oil field workers may suffer injury if their hands or fingers are caught between the rod clamps when the rods drop.
Fluid pound is a condition that occurs when the fluid level in the well bore is not high enough to allow the sucker rod pump to completely fill. Traditionally, clocks, or mechanical timers, have been used to start the pumpjack for a predetermined amount of time, then to stop it for a predetermined amount of time. The fallacy of this method is that the fluid entry into the well bore may not always be at a uniform rate. Because the clock (mechanical timer) cannot react to the changing well bore conditions, the pumpjack may run too long and create a condition called fluid pounding which is a condition that occurs when the fluid level in the well bore is not high enough to allow the sucker rod pump to become completely filled. Conversely, if the pumpjack does not run long enough, the well is not being pumped to its full potential. Unfortunately, an economical and easily operated manner of solving these problems has proven to be elusive.